1. Field of the Invention
The present invention generally relates to a control apparatus for an internal combustion engine (hereinafter also referred to simply as the engine) which apparatus is designed for performing identification of cylinders of the engine and control thereof on the basis of crank angle pulse signals related to a crank shaft of the engine mounted on a motor vehicle and cylinder identifying pulse signals related to a cam shaft of the engine. More particularly, the present invention relates to a control apparatus for an internal combustion engine in which the crank angle pulse signal contains unequi-interpulse intervals in correspondence to reference crank angle positions (hereinafter also referred to simply as the reference positions) in a pulse train composed of a large number of equi-interval pulses.
In particular, the present invention is concerned with a control apparatus for the internal combustion engine which apparatus is so designed as to prevent erroneous ignition and fuel injection controls ascribable to erroneous identification of the reference positions and the cylinders which may be brought about by repetitive on/off manipulation of a cranking switch (hereinafter also referred to as the starter switch) in the course of an engine starting operation.
2. Description of Related Art
In general, in the internal combustion engine such as the engine for an automobile or a motor vehicle, it is required to detect on a cylinder-by-cylinder basis the crank angle positions corresponding to rotational positions of the engine in order to control optimally the fuel injection timing as well as the ignition timing for a plurality of engine cylinders in dependence on the engine operation state or condition.
Such being the circumstances, in the conventional control apparatuses for the internal combustion engine known heretofore, electromagnetic sensors are provided in association with a crank shaft and a cam shaft, respectively, of the engine to thereby make available the crank angle pulse signals (also referred to as the crank angle pulses) indicating reference positions for the individual cylinders, respectively, and cam signals (also referred to as the cylinder identifying pulse signals or simply as the cylinder identifying pulses) for identifying discriminatively a specific cylinder and individual cylinders, respectively.
Further, a control unit (referred to as an electronic control unit or ECU in abbreviation) is provided which is so arranged as to discriminatively determine or identify the individual cylinders on the basis of the crank angle pulse signals and the cylinder identifying pulse signals while determining discriminatively the reference positions on a cylinder-by-cylinder basis to thereby arithmetically determine various control quantities for realizing the fuel injection control and the ignition timing control with high accuracy and reliability.
To this end, a crank angle position detecting means is provided which is composed of a disk which is rotatable in synchronism with the crank shaft and a crank angle sensor which is disposed in opposition to the disk. For generating the crank angle pulses which correspond to a plurality of crank angle positions, respectively, the disk is provided with a plurality of detecting members in the form of ring gear teeth with equidistance therebetween along the outer periphery of the disk.
The crank angle sensor is designed to generate as the output signal thereof the crank angle pulses at every predetermined angle (e. g. 10xc2x0 in terms of the crank angle, represented hereinafter as 10xc2x0 CA) upon every passing-by of the ring gear teeth (projections) formed in and along the outer peripheral edge of the disk rotating synchronously with the crank shaft.
Thus, the control unit can determine the reference positions (e.g. B75xc2x0 CA (i.e., 75xc2x0 CA before the top dead center or TDC) and B5xc2x0 CA (i.e., 5xc2x0 CA before the TDC) ) by detecting unequi-interpulse intervals in the crank angle pulse train by measuring the periodical intervals at which the crank angle pulses are generated.
To this end, the detecting member of the crank angle position detecting means is provided with a tooth dropout section (i.e., a peripheral portion in which no tooth is formed) which extends over an angular range of e.g. 30xc2x0 CA at the reference position of each cylinder (e.g. position 75xc2x0 or 5xc2x0 CA before TDC in the compression stroke) so that the unequi-interpulse interval makes appearance in the train of the crank angle pulses generated at an equi-interpulse interval.
Further, the cam shaft which rotates at a ratio of 1/2 relative to the rotation of the crank shaft is provided with a crank angle position detecting means which is constituted by a disk rotatable in synchronism with the cam shaft and a cylinder identification sensor disposed in opposition to the disk. The cylinder identification sensor is so designed as to generate as the output signal thereof the cylinder identification information corresponding to the specific cylinder or individual cylinders.
In this manner, the control unit can detect the reference position corresponding to the partial pulse dropout portion or section (i.e., unequi-interpulse interval) in the crank angle pulse train to thereby realize the cylinder identification with high accuracy and reliability on the basis of combination of the crank angle pulses and the cylinder identifying pulses.
To say in another way, the control unit is capable of discriminatively identifying the individual cylinders on a real-time basis in response to the pulse dropout portions corresponding to the reference crank angle positions and the cylinder identifying pulse signals by detecting on a real-time basis the reference positions on the basis of the crank angle pulse signals.
In this conjunction, it is noted that the unequi-interpulse intervals (i.e., pulse dropout portions) in the crank angle pulse train can be detected correctly and relatively easily so long as the internal combustion engine rotates in the forward direction in a substantially steady state. However, in the course of the cranking operation carried out for starting the operation of the engine, there may arise such situation that the cranking operation is interrupted or stopped before the engine is actually put into operation (i.e., before the engine operation is started) because the starter is manipulated manually.
If the cranking operation should stop before the engine operation is started, then the driving torque is no more transmitted to the internal combustion engine from the starter. Consequently, the piston in the cylinder which is in the compression stroke would not completely be pushed up to the top dead center (TDC).
In that case, the piston may move downwardly from the crank angle position immediately before the TDC position, thus incurring possibly reverse rotation of the engine.
In this conjunction, it is noted that at the time point when the rotation of the internal combustion engine changes from the forward direction to the reverse direction (i.e., at the topmost position of the piston), the engine is caused to stop momentarily or transiently. As a result of this, the input period of the crank angle pulse will become longer. As a consequence, there may unwantedly arise such situation that the period detected at this time point is erroneously recognized as an unequi-interpulse interval or dropout portion (representing the reference position) in the crank angle pulse train.
Furthermore, in the case where the piston can barely clear the top dead center (TDC) in the compression stroke under inertia after the cranking operation has been stopped before the engine operation starts, the engine will then behave as if it stopped momentarily at the top dead center (TDC), which results in that the crank angle pulse period becomes longer at or around the top dead center (TDC) to such extent that the unequi-interpulse interval or dropout portion will erroneously be determined, giving rise to another problem.
Besides, in the case where the cranking operation is again started in the course of inertial rotation after stoppage of the cranking operation, the engine is driven again by the starter. In that case, since in the inertial rotation, the engine speed decreases gradually to zero, the crank angle pulse period becomes longer correspondingly. However, when the cranking operation is restarted, being driven by the starter, the engine rotation speed increases again, as a result of which the crank angle pulse period becomes shorter.
In this conjunction, it is however noted that when the engine rotation has reversed immediately before the cranking operation is started again, the engine stops temporarily upon transition from the reverse rotation to the forward rotation because the engine is forced to rotate in the forward direction when the cranking operation is restarted. Consequently, the crank angle pulse period will become longer to be erroneously detected as the unequi-interpulse interval or dropout portion.
As is apparent from the above, when the starter switch is repetitionally turned on and off (i.e., when the cranking operation is repetitively started and stopped) upon starting of the engine operation (i.e., before the engine is put into operation), the interval in which the crank angle pulse period becomes longer may make appearance to be erroneously detected as the unequi-interpulse interval or dropout portion.
If the unequi-interpulse interval (dropout portion) should erroneously be detected or identified by the electronic control unit as the reference position, then the detected crank angle position will become deviated from the actual position, which will then result in that the cylinder identification is performed with reference to the deviated crank angle position, incurring thus erroneous cylinder identification because of the deviation from the unequi-interpulse interval or dropout portion intrinsically dedicated for the identification of the cylinder.
Needless to say, when the crank angle position and the cylinder are detected and identified erroneously, the angular positions for controlling the fuel injection timing and the ignition timing will then differ from the normal or proper control positions. As a result of this, such undesired event as backfire, engine lock or the like may take place, damaging seriously the engine in the worst case.
As can now be appreciated from the foregoing, with the conventional control apparatus for the internal combustion engine, it is certainly possible to detect correctly the unequi-interpulse interval (corresponding to the tooth dropout section mentioned hereinbefore) without any appreciable difficulty so long as the engine rotates in the forward direction in the relatively stable state. However, when the cranking operation is repeated in the engine starting phase (i.e., before the engine is actually put into operation), the crank angle pulse period becomes unstable or nonuniform, as a result of which the unequi-interpulse interval may erroneously be detected, rendering it impossible to control the engine cylinder with sufficient accuracy and reliability, incurring undesirably occurrence of the backfire, engine lock or the like event which may eventually lead to serious damage of the engine, giving rise to problems.
In the light of the state of the art described above, it is an object of the present invention to provide a control apparatus for an internal combustion engine of a structure which is improved such that erroneous detection of the crank angle position and the cylinders can be prevented and thus erroneous control of the ignition and the fuel injection can positively be suppressed by detecting the driving/non-driving state of the starter and by inhibiting the cylinder identification information already acquired from being used in a succeeding cylinder identification process when the starter switch is turned on/off in the course of starting the operation of the engine.
Another object of the present invention is to provide a control apparatus for an internal combustion engine which can ensure enhanced reliability for the cylinder identification and the cylinder control by inhibiting the cylinder identification from being validated again until the normal rotational state of the engine can be detected.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention an improved control apparatus for an internal combustion engine.
The control apparatus includes a starter driven for rotation upon starting operation of an internal combustion engine, a crank shaft directly coupled to the internal combustion engine for corotation therewith, a crank shaft disk rotatable in synchronism with the crank shaft, angular position detecting members provided with equidistance therebetween along an outer peripheral edge of the crank shaft disk so as to correspond to a plurality of crank angle positions of the internal combustion engine, dropout sections for forming unequidistance portions partially in the angular position detecting members so as to correspond to reference crank angle positions, respectively, of cylinders of the internal combustion engine, a crank angle sensor disposed in opposition to the angular position detecting members for generating crank angle pulse signals representing the crank angle positions, a cam shaft rotatable at a rotation ratio of 1/2 relative to the crank shaft, a cam shaft disk rotatable in synchronism with the cam shaft, cylinder identification information detecting members provided along an outer periphery of the cam shaft disk so as to made available cylinder identification information of the internal combustion engine, a cylinder identifying sensor disposed in opposition to the cylinder identification information detecting members for generating cylinder identifying pulse signals representing the cylinder identification information, and an electronic control unit for controlling each of the cylinders of the internal combustion engine on the basis of the crank angle pulse signals and the cylinder identifying pulse signals.
The electronic control unit includes a cylinder identifying means for discriminatively identifying each of the cylinders of the internal combustion engine by making use of the crank angle position based on the crank angle pulse signals and the cylinder identification information based on the cylinder identifying pulse signals, a crank angle signal period arithmetic means for arithmetically determining input periods of the crank angle pulse signals as crank angle pulse signal periods, a starter drive detecting means for detecting changeover of driving state of the starter, a rotation speed detecting means for detecting rotation speed of the internal combustion engine, and a cylinder identification information invalidating means responsive to changeover of the starter driving state between driving state and non-driving state in an operation state in which the crank angle pulse signal period is longer than a predetermined period and in which rotation speed of the internal combustion engine is lower than a predetermined speed, for thereby invalidating the cylinder identification information detected before changeover of the starter driving state to inhibit the cylinder identification information from being employed in a succeeding cylinder identification.
By virtue of the arrangement of the control apparatus for the internal combustion engine described above, when the on/off operation of the starter switch is detected in the course of starting the operation of the engine, erroneous detection of the crank angle position and the cylinders can be prevented and thus erroneous control of the ignition and the fuel injection can positively be suppressed by inhibiting the cylinder identification information already detected from being employed in a succeeding cylinder identification.